Trevor Silvester in his book, Wordweaving, develops The Matrix Model to map the mental steps the unconscious mind from receiving a stimulus to completion of the response.

People familiar with the APET model developed by Ivan Tyrell and Joe Griffin, will recognise some similarities with this model, the main difference is that a couple of additional steps are added, making the model cyclical and a more systemic approach to therapy follows from this.

The Matrix Model has six steps:
Stimulus: The stimulus can be an external event, such as seeing a spider, or internal mental activity, such as remembering or imagining something.
Memory Matrix: The pattern matching done by the mind- comparing the stimulus to existing memory patterns.
Emotion: When the pattern match generates an emotional response.
Response: The response will by a 'thought sequence' and/or behaviour based on the meaning of the pattern match.
Termination: The ending of the thought sequence and behaviour.
Evaluation: An unconscious appraisal of the event to confirm or deny its validity.

So for an arachnophobe, experiencing a phobic response to spider, the unconscious appraisal would be that the response had been effective in ensuring the person had avoided the perceived threat.